planetary

Concise Oxford English Dictionary © 2008 Oxford University Press:
planet/ˈplanɪt/

▶noun a celestial body moving in an elliptical orbit round a star.

■ (the planet) the earth.

■ chiefly Astrology & historical a celestial body distinguished from the fixed stars by having an apparent motion of its own (including the moon and sun).

– phrases
what planet are you on? Brit. informal used to indicate that someone is out of touch with reality.

– derivatives
planetary adjective,
planetologist noun,
planetology noun.

– origin ME: from OFr. planete, from late L. planeta, planetes, from Gk planētēs ‘wanderer, planet’, from planan ‘wander’.